Particulate material has been utilized in various vessels. For instance, several attempts have been made to decrease the thermal conductivity of a vessel (e.g., a window, skylight, etc.) by filling the internal volume of the vessel with a particulate material. Particulate material presents unique handling challenges, however, particularly with regard to filling the internal volume of a vessel. For example, due to several factors, such as the humidity of the container in which the particulate material is stored, particulate materials stored in bulk often have a tendency to agglomerate into relatively large agglomerates, which can make the handling of the particulate material much more difficult. These agglomerates can then impede the flow of the particulate material through the equipment used to handle the particulate material and into the internal volume of the vessel. Indeed, the process of filling the internal volume of a vessel becomes even more complicated when the dimensions of the agglomerates formed by the particulate material are larger than the opening in the vessel through which the internal volume is to be filled. Thus, known methods and apparatus for filling the internal volume of a vessel with a particulate material often are deleteriously affected by the agglomeration of the particulate material. Attempts to meet the unique problems encountered in handling large amounts of particulate material have met with varying success.
Furthermore, the handling of large amounts of particulate material often generates relatively large amounts of static electricity and causes the individual particles to become electrostatically charged. Apart from the hazards posed to equipment from such large amounts of static electricity, the electrostatic charge of the individual particles can cause the particles to agglomerate even further. Moreover, the electrostatic charge of the individual particles can cause the particles to adhere to the surfaces of the machines used to handle the particulate material, or it can cause the individual particles to adhere to the interior surfaces of the vessel, thereby impeding movement of the particulate material into the internal volume of the vessel. Despite the negative effects of such static electricity, none of the known methods and apparatus for filling the internal volume of a vessel has effectively addressed the problem of static electricity production during the filling of such vessels.
As known to those of skill in the art, a particulate material has a tendency to settle at a certain density (or a relatively narrow range of densities) when the particulate material is simply poured into a volume, such as the internal volume of a vessel. This density of the particulate material within the vessel that results from a simple pour into the vessel is generally referred to as the pour density. It is often desirable, however, to fill the internal volume of a vessel with a particulate material at a density that is higher than this pour density. For instance, filling the internal volume of a vessel with a particulate material at a relatively high density (e.g., a density higher than the pour density of the particulate material) can often dramatically improve (e.g., decrease) the thermal conductivity of the vessel as compared to a vessel that has been filled with the same particulate material at its pour density. While known methods and apparatus for filling the internal volume of a vessel can be used to fill the internal volume of a vessel with a particulate material at a density that is approximately equal to its pour density, these processes and apparatus cannot effectively be used to fill a vessel with a particulate material at a density that is substantially higher than the pour density of the particulate material.
Accordingly, a need exists for a method and apparatus for filling the internal volume of a vessel with a particulate material which addresses the foregoing and other problems not addressed by prior methods and apparatus. The invention provides such a method and apparatus. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.